Guardian防风雨电话机WRT-20-H Product Features • Membrane Keypad/Curly Cord/Volume Control   on Keypad • Magnetic reed hook switch to reduce parts subject    to wear • Encapsulated circuitry impervious to water    and particles • Nylon hinge to prevent jamming caused by salt    or corrosion  • Spring-loaded door for automatic closure  • Surge arrestor to prevent voltage spike damage • Heavy duty industrial handset • Volume control to ensure communication in    noisy environments • Electret noise reducing microphone for clear    communication • Service temperature range from -40˚ to +140˚F    ( -40˚ to +60˚C ) • Waterproof connections & stainless steel fittings    for longer life • Compact durable enclosure with mounting plate for    easy mounting • Modular parts for easy service • Hearing aid compatible • Electronic ringer for reliability • Yellow enclosure for high visibility. Optional Grey    enclosure and other custom options available • Weather, dust & corrosion resistant • Tone or pulse dialing for universal configuration • Easily connected to any single line analog CO or    PABX telephone line • Powder coated, corrosion protected steel faceplate • Front access plate for ease of hook-up Guardian 墙式电话机DTT-50 Desktop/Wall Mount Phone Guardian 台式电话机DTT-50 Guardian 工业电话机DTT/DTRDTT-50 DTT Guardian铸铝外壳电话机ACT-30 Guardian 防水/防尘的食品工业电话FIT-80 Food Industry Guardian 防水/防尘工业电话FIT-80,MFT-30,ACT-40 ACT-40 Guardian 电话机Cast Aluminum Guardian电话机WRT-10 Guardian 电话机WRT系列WRT-10,WRT-20 美国原装进口Guardian室内防水电话机 SCR-11